Tensioner reflector sheet with press forms

ABSTRACT

A reflector of radiation that is formed in its place of intended use by anchoring a sheet of the reflective material between fixed abutments and thrusting spaced press forms into contact with the sheet with sufficient force to conform the sheet elastically to the contour of the press forms.

United States Patent Medley [54] TENSIONER REFLECTOR SHEET WITH PRESSFORMS [72] lnventor: Richard C. Medley, Niles, ll].

[73] Assignee: Crou'se-Hinds Company, Syracuse,

[22] Filed: April 24, 1969 [21] Appl. No.: 818,883

52 us. 01. ..240/41.3s E, 240 415, 240/103 R 58 Field of Search..240/36, 41.35, 103, 41.35 E,

[56] References Cited 2 UNITED STATES PATENTS 922,958 5/1900 Ryan....240/36 1 51 Aug. 22, 1972 2,339,l0(l 1/1944 Netting ..240/ l 03 X2,522,230 9/1950 Komulaine ..240/lO3X 3,099,403 7/1963 Strawick ..240/103 B Primary Examiner-Joseph F. Peters, Jr. Attorney-Anderson, Luedeka,Fitch, Even and Tabin ABSTRACT A reflector of radiation that is formedin its place of intended use by' anchoring a sheet of the reflectivematerial between fixed abutments and thrusting spaced press forms intocontact with the sheet with sufiicient force to conform the sheetelastically to the contour of the press forms.

6 Claim, 5 Drawing Figures Patented Aug. 22, 1972 2 Sheets-Sheet}INVENTOR RICHARD C. MEDLEY AT TYS.

FIG 4 FIG?) Patented Aug. 22, 1972 3,686,495

2 Sheets-Sheet 2 a g m S l a I on H l I WW, I n

INVENTOR RICHARD C. MEDLEY ATTYS.

This invention relates to reflectors of radiation and particularly to areflector which is caused to assume a predetermined geometric shape asan incident to its installation into its use position. It is hereillustrated and described in connection with a luminaire, but its usemay well extend to other projectors and receivers of radiated orbroadcast energy. v It is an observed fact that metallic reflectors inluminaires or the like that are subjected to high temperatures in normalusage exhibit some tendency to distort in use, the effect beingparticularly noticeable in those kinds of reflectors that might bedescribed as straightline generated in geometric shape. This may be dueto the fact that asurface curved with respect to only one referenceplane is more subjectto buckling than is a surface of multiple-axiscurvature, or it may be that distortion from whatever cause is morenoticeable on the usual intercept of visible radiation beamed from aluminaire having a reflector of the straight-line generated or linearelement type.

In any case, it is the object of this invention to overcome thedistortion tendency, and to do so by actually forming the reflectorsurface in situ, i.e., at the site of the intended use.

In the drawings:

F IGS. 1a and 1b in succession illustrate diagrammatically the formingof the desired optical contour in a reflector surface by its assemblywith press forms which, in the assembly of the device, causes thereflector sheet to assume the desired geometric shape;

FIG. 2 is a fragmentary perspective view of a luminaire whose outercasing is partially broken away to show a reflector in accordance withthe invention;

F IG. 3 is a side elevation of a complete luminaire embodying theinvention in a double or vertically stacked arrangement that is moreapparent from FIG. 4; and

FIG.'4 is a front elevation of the luminaire shown in FIG. 3.

The sequence of illustrations of FIGS 1a and 1b indicatediagrammatically how this invention is utilized. In essence, itspractice contemplates spaced opposed abutments which are fixed relativeto one another. Between the two abutments there is suspended a sheet 12of flexible material, for example metal, at least one surface of whichis highly polished, in the case of a luminaire application, or otherwiserendered reflective with respect to the particular radiation with whichthis scheme is to be employed. This sheet need have no previous forminginsofar as its optical character is concerned, the sheet 12 in theillustrations of FIGS. la and lb, having merely been formed slightly atits opposite edges to form mounting flanges 14 which are punched tofacilitate assembly of the reflector sheet with the abutments in anyconvenient manner, for example, by rivets, screws, bolts, or the like.

The curve, therefore, which is assumed by the sheet 12 in theillustrations of FIG. la is not any particular curve, but whatever curvethe sheet may take upon having been flexed from a flat condition inbeing assembled with the abutments 10. It may be equally feasible,however, to preform the sheet, if desired, to give it an initialcurvature which may approach as nearly as one might wish to the desiredfinal form, which is im- 2 posed upon the-sheet, and retained therein,by a pair of opposed curved press forms 16.

The press forms are machined accurately to the desired final shape-ofthe surface of the sheet with which they are engaged, the press forms 16illustrated in FIGS la and lb'having a parabolic contour. The length ofthat portion of the sheet which extends between the abutments is atleast slightly greater than the mating surface of the press form inorder that the resistance of the sheet, i.e., its reaction to the forceexerted upon the sheet by the press forms, is carried to the anchoringabutments only through the sheet itself, inasmuch as it is desired thatthe sheet be placed in tension between the abutments in order to assureconformance to the contour of the press form. The forces acting on thesystem of press form 16, reflector sheet 12, and anchoring abutments 10,are illustrated by the arrows in FIG. 1b.

When the opposed press forms are assembled with the reflector sheet asindicated in FIG. 1b, the mating surface of the reflector sheet 12assumes the shape of the press form 16, which is inserted withsufficient force to achieve this result. The amount of force em- .ployedis such as to stress the sheet material only within its elastic limit,as it is preferred to maintain the sheet in tension between theabutments, i.e., to avoid such stretching as might interfere withconformance of the sheet to the press forms at some later time in thelife of the device, e.g., as the material ages, or under such design oroperating conditions as might serve either to relieve the tensile stressin the sheet, or conversely, to cause that stress to exceed the elasticlimit of the sheet material.

For example, in a particular application using a linear light source 18such as is indicated in FIGS. 2 and 4, which is of the type referred tocommonly as the quartz-iodine" type, the temperature of the lamp basesunder standard ambient conditions rises to 350 C. This heat sourceinduces high temperatures in the surroundings, not only by virtue ofconduction from the lamp itself and its appurtenances, but also bydirect radiation from the source, which as a substantial element ofradiation of a frequency lower than the visible spectrum. If the designof the luminaire is such as to promote substantial differences oftemperature between the press form and the sheet which constitutes thereflector, or if the materials employed have substantially differentrates of thermal expansion, the initial stress may be quite important.For example, if the reflector sheet were to expand more than the pressform, the tensile force at high temperature might be insufficient tomaintain the conformance of the reflector sheet to the press forms.Conversely, if the press forms were to expand linearly more than thesheet, they could induce tensile stress of magnitude sufficient to givethe sheet a permanent set, and thus to interfere with its conformance tothe press form at lower temperatures.

It is accordingly desired to maintain the stressed conformance in thesheet at all times and under all conditions of operation within theelastic limit of the sheet material, a condition which is obviously mosteasily achieved under most circumstances by employing as reflector sheetand press form materials substances having the same thermal coefficientof expansion. In the illustrated application, I have found it quitesatisfactory indeed to employ aluminum alloys of substantially identicalthermal coefficients of expansion.

A practical physical structure for achieving the aforementionedconditions is illustrated by the luminaire 18 shown in FIGS. 2, 3 and 4.As illustrated, the luminaire comprises a rectangular box which enclosestwo substantially identical reflector systems of the kind just describedin principle. They are stacked one above the other in vertical array,and project the luminous radiation from two pencil-like light sources 20of the quartz-halogen type outwardly through a flat lens 22 which may beoptically null or optically directional. The lens is secured in aperipheral frame 24, which is formed of T-shaped cross section, hingedalong one of its long edges at 26 to the rectangular box, and held tightto the box along its opposite long edge by means of toggle clamps 28 ofthe general type common in luggage.

The box serves as structure as well as outer casing, and is formed ofaluminum sheet which is bent to shape and flanged at its front edges(FIG. 2) to form a seat 30 for the lens frame. For convenience ofmanufacture, the box of the illustrated luminaire is made in threepieces, a body sheet 32 which forms the back wall and sidewalls, a topsheet 34 and a bottom sheet 36 which are assembled to the body sheet bymeans of rivets through lapped seams. To aid in shedding rain, thedownturned flanges of the top sheet are on the outside of the bodysheet, whereas the upturned flanges of the bottom sheet are on theinside of the body sheet.

Also shown in FIGS. 3 and 4 are the flanged enclosing cups 38 which aresecured to the sidewalls of the luminaire to cover holes therein alignedwith the axis of the tubular light source, thereby to provide additionalclearance for the tube sockets. The cups 38 are secured to the casingbymeans of rivets, and the flanges of the cups are gasketed to keep outthe elements.

Extending rearwardly from the back wall of the luminaire casing is ajunction box 40 to which the leads of the lamp sockets are brought forconnection to a supply conductor 42 from a suitable power source.

The entire luminaire is adjustably supported in a yoke 44 in which it ispivoted by means of sidewardly extending trunnions 46 upon which theluminaire may swivel. Any desired position of adjustment is maintainedby tightening the nuts on the threaded terminal portions of thetrunnion. A protractor 48 is provided at the swivel for convenientrestoration of any preset alignment that may necessarily be disturbed inthe course of maintenance. A mounting bracket 50 on the base or crossleg of the yoke is likewise provided with a main pivot hole 52 as wellas an arcuate slot 54 thereabout for pivotally mounting the yoke upon asuitable mating support, and for maintaining any desired angularadjustment.

In the case of directive illumination of this sort, the necessaryalignment can be achieved by predetermined angulation from establishedreference planes. It is also useful, however, to align luminaires ofthis kind by visual sighting, and for that reason, a bracket 56 ismounted on the outer casing for receiving a telescopic sight of the kindused in riflery.

The earlier-described reflector arrangement of FIG. 1 is mounted uponinterior peripheral framing 58 which is secured to the inside faces ofthe side and top and bottom walls of the outer casing by means ofrivets. The framing is of angle-shaped cross section to provide anattaching flange 60 to secure the frame in place and to add to the beamstrength of the framing, the other angular flange 62 providing seats forthe mounting of the press forms 16, as well as anchoring abutments 10for the secured ends of the reflector sheet.

Because of the stacked, double arrangement in the illustrated case, thereflector frame 58 is divided longitudinally into two parts by a pair ofcross members 64 of angle section that are joined back-to-back by stitchrivets which unite and strengthen the assembly. The flanges of thecross-members 64 and the end members that are parallel to the plane ofthe frame provide the anchorages 10 for the reflector sheets 12 whichare secured to those flanges by means of rivets, of which there arethree at each secured edge in the illustrated case.

The press forms 16 in the illustrated case are also formed of aluminumalloy plate of substantially greater thickness than the reflector sheets12, i.e., about oneeighth inch thick. As earlier indicated, the specificplates shown are parabolic in form, the parabolic contour ending at achord perpendicular to the focal axis to form a straight front edge 66.At the center of the front edge of the press form, there is an angleflange 68 with a central hole through which there is passed a machinescrew 70 threaded in a suitable hole in the facing flange 62 of thereflector frame 58. The tightening of this screw provides a thrust inthe direction of the focal axis of the parabolic press form, causing itto tighten its engagement with the reflector sheet as earlier described,and causing the sheet to assume the contour of the press form. The pressform engages the reflector sheet a short distance inwardly from thebowed edge of the sheet, (see FIG. 2) and the desired perpendiculararray of the press form with respect to the sheet is maintained by meansof a small tongue 71 which protrudes from the curved surface of thepress form 16 as an extension of the focal axis to be received in asuitable rectangular positioning slot in the reflector sheet. (See FIGS.1a and 1b).

In the illustrated luminaire, it was found desirable to re-direct lightemitted sidewardly from the light source by means of plane sidereflectors 72 extending at an angle into the field of the parabolicreflector. These are omitted in FIG. 2 as they would have obscured thepress forms, but are shown in FIG. 4. The side reflectors are secured inplace by means of a couple of screws received in the two flanking holes74 on the turnedover flange 68 of the press form, and the sidereflectors themselves are provided with rectangular holes 76 throughwhich the pencil-like light sources 20 can be inserted into theirsockets 78 which are mounted on the press forms themselves inpositioning holes 80. Those portions of the lamp sockets which receivethe lamp bases float in spring mountings so that the light source may beremoved from the sockets by sequential endwise movements of the tube.

With the foregoing arrangement I have found it possible to generate andto maintain the desired optical form of the reflector with greateraccuracy and reliability than has heretofore been achieved by othertechniques of forming reflectors of metal.

What is claimed is:

1. A reflector of radiation comprising a flexible sheet having areflecting surface, a frame member providing opposed abutrnents spacedapart a fixed distance less than the distance between opposite edges ofsaid sheet when unflexed, said opposite edges of said sheet beingsecured to said opposed abutments to arch said sheet between saidabutments, a press form having a convex edge engaged with the concavesurface of the sheet, and means connecting said frame and said pressform and urging said press form against said sheet with force suflicientto place said sheet in tension between said opposed abutments and toconform the sheet to the contour of the press form thereby to determinethe contour of the reflective surface of the sheet.

2. The reflector of claim 1, in which the flexible sheet is metal andthe tensile stress induced therein by the press form is maintainedwithin the elastic limit of the said metal.

3. The reflector of claim 1, in which the flexible sheet is metal, andin which the press form and the sheet have substantially the samecoefficient of thermal expansion.

4. The reflector of claim 1, in which the flexible sheet is alight-colored ductile metal and has on its concave surface a specularfinish, said reflector including a second press form of the same contouras the first and spaced from the first but likewise so engaged with thesheet that said two press forms determine the optical character of saidreflective sheet between the two press forms, and in which said pressforms have substantially the same coefiicient of thermal expansion assaid sheet.

5. In a luminaire having a reflector for projecting light from anessentially linear light source, a frame providing abutments fixedrelative to one another and in flanking relation to the axis of thelight source, a sheet of metal arched between and secured to saidabutments and having on its concave surface a light! reflective finish,a pair of press-forms engaged with the concave surface of the sheet atopposite ends of the light source, screws connecting said press formsand said frame to urge said forms against said sheet with forcesufiicient to place said sheet in tension between said abutments and toconform the sheet to the contour of the press forms thereby to determinethe optical contour of the light-reflective surface of the sheet.

6. .In a luminaire according to claim 5, the frame ineluding a caseenclosing the reflector and having a lens through which the lightemitted from the source is projected.

1. A reflector of radiation comprising a flexible sheet having a reflecting surface, a frame member providing opposed abutments spaced apart a fixed distance less than the distance between opposite edges of said sheet when unflexed, said opposite edges of said sheet being secured to said opposed abutments to arch said sheet between said abutments, a press form having a convex edge engaged with the concave surface of the sheet, and means connecting said frame and said press form and urging said press form against said sheet with force sufficient to place said sheet in tension between said opposed abutments and to conform the sheet to the contour of the press form thereby to determine the contour of the reflective surface of the sheet.
 2. The reflector of claim 1, in which the flexible sheet is metal and the tensile stress induced therein by the press form is maintained within the elastic limit of the said metal.
 3. The reflector of claim 1, in which the flexible sheet is metal, and in which the press form and the sheet have substantially the same coefficient of thermal expansion.
 4. The reflector of claim 1, in which the flexible sheet is a light-colored ductile metal and has on its concave surface a specular finish, said reflector including a second press form of the same contour as the first and spaced from the first but likewise so engaged with the sheet that said two press forms determine the optical character of said reflective sheet between the two press forms, and in which said press forms have substantially the same coefficient of thermal expansion as sAid sheet.
 5. In a luminaire having a reflector for projecting light from an essentially linear light source, a frame providing abutments fixed relative to one another and in flanking relation to the axis of the light source, a sheet of metal arched between and secured to said abutments and having on its concave surface a light-reflective finish, a pair of press-forms engaged with the concave surface of the sheet at opposite ends of the light source, screws connecting said press forms and said frame to urge said forms against said sheet with force sufficient to place said sheet in tension between said abutments and to conform the sheet to the contour of the press forms thereby to determine the optical contour of the light-reflective surface of the sheet.
 6. In a luminaire according to claim 5, the frame including a case enclosing the reflector and having a lens through which the light emitted from the source is projected. 